The present invention relates to a wet development apparatus for a recording machine such as an electrophotographic copying machine or an electrophotographic printer, and which is used to render visible an electrostatic latent image using a wet developer composed of an electrically insulating carrier liquid and charged grains dispersed in the liquid.
In a conventional wet development apparatus, an electrostatic latent image carrier is moved along a pan-shaped electrode containing a developer so that the developer is applied to the carrier, as disclosed in, for example, an Examined Japanese Patent Publication No. 51466/87. In another type of a conventional wet development apparatus, as disclosed in Examined Japanese Patent Publication No. 23792/69, a development section and a developer tank are connected to each other through a vacuum pump so that a developer is circulated out of a slender opening of the development section.
In Unexamined Japanese Utility Model Publication No. 84394/88, an image is developed by discharging a developer from a slot of an electrode plate, which is opposed to an electrostatic latent image carrier across a small gap, so that charged grains cling to the carrier due to an electric field between the carrier and the electrode plate.
In Unexamined Japanese Utility Model Publication No. 120058/80, a developing method, in which an elastic roller is brought in pressure contact with a photosensitive drum, is taught. A developer is carried to the photosensitive drum in such a manner that the elastic roller is dipped into the developer accommodated in a developer tank so as to adhere the developer onto the outer peripheral surface of the elastic roller.
In the above-mentioned conventional wet development apparatus, a developer, having a low density, accommodated in a developer tank is supplied in such a manner that a photosensitive drum is dipped into the developer in the tank, so that a vapor of a carrier liquid in the developer is discharged into the atmosphere. A bad odor is generated from the vapor, so that an environment is influenced by the odor.
In the above-mentioned conventional wet recording machines, the coloring agent of the wet developer, which is generally constituted by charged grains of a toner made of a pigment and a resin, clings to the electrostatic latent image carrier through electrophoresis. Therefore, a large amount of developer is needed for development. This creates a problem in that a large space is required for storing the developer, particularly the carrier liquid portion. Accordingly, a large wet development apparatus is required. Since the electrophoretic velocity of the coloring agent depends on the viscosity of the developer, the viscosity must be kept low to make the velocity high. For this reason, the charged grains of the toner need to be dispersed in a large quantity of a carrier liquid to make the viscosity of the developer low. Since the carrier liquid does not participate in finally forming a visible image on recording paper, the liquid needs to be evaporated or be recovered and discarded. This creates yet another problem.
If development is to be performed with different color developers in the conventional development apparatus, the development device of the apparatus needs to be provided with a "put-aside" mechanism for changing the different color development devices, which operation is time consuming. This too is a problem.